1. Field of Invention
The invention relates to a communications link and more particularly to a micro range RF communications link between a moving device and at least one access point positioned along a predefined path of motion for the moving device.
2. Description of Related Art
Data communication between various parts or components of an industrial machine or between a plurality of industrial devices is integral to a control and management system for industrial manufacturing. As a result, the type of communications link becomes extremely important. Factors that are considered when selecting a type of communications link are data transmission rate, range, battery life, security, cost, quality of service, and interoperability.
One type of communications links is a wired cable. A cable is attached to each part(s) of the machine and to each machine to facilitate or enable communication. However, the use of cables causes a significant overhead for installation, maintenance and troubleshooting. For example, several of the machine parts are in a difficult location to attach a cable or replace the cable that requires a significant cost for the installation and maintenance. Additionally, as the machine is used, the cables become damaged and must be replaced. The machine(s) must be stopped to replace the cable, causing the manufacturing process to be halted. Further, network routing would require significant overhead and/or a separate device dedicated to control routing communication signals between devices. Additionally, even if only a small section of the cable is damaged, the entire cable will be replaced.
Another type of communications link is a standard wireless antenna. In the last few years, many wireless connectivity standards have emerged. These technologies enable users to connect a wide range of computing and telecommunications devices easily and simply, without the need to buy, carry, or connect cables. These devices have eliminated the need to purchase additional or proprietary cabling to connect individual devices, thus creating the possibility of using mobile data in a variety of applications. There are many standards such as Bluetooth, IrDA, Home RF, and IEEE 802.11.
However, the uncoordinated transmission of wireless signals leads to signal interference. The transmission of control information or data between various moving parts and a central base station requires a long range communications link. However, an industrial environment is very noisy and is rampant with interference by electromechanical devices in the area. Additionally, wireless devices transmitting RF signals in the same area contribute to transmission failures.
Accordingly, there is a need to provide a communications link that overcomes the problem of signal interference, reduces the cost and simplifies the maintenance for the communications link.